Heat exchanger with crossing helicoidal tubes



Aug. 15, 1967 ARPAD ARANYI ETAL 3,335,790

HEAT EXCHANGER WITH CROSSING HELICOIDAL TUBES Filed March 18, 1966Arpa'cl Ara'nyi IN VE N TORS Attorney Guszfa'v Gergely United StatesPatent 6 Claims. 61. 165-109 ABSTRACT OF THE DISCLOSURE Heat exchangerhaving a cylindrical housing with an inlet and an outlet for a firstfluid and substantially completely filled with a packing formed bycrossing coaxial layers of oppositely turned helicoidal tubes formingwithin the channel of the housing baflles with relatively narrowinterstitial openings imparting turbulence to the entire mass of liquidpassing through the channel. The tubes 7 surround a core.

Our present invention relates to a heat exchanger in which two fluids ofinitially different temperatures pass in close proximity to each other,but along different paths, for the purpose of heating or cooling one ofthe fluids at the expense of the other.

A typical field of application of such heat exchangers is in the coolingof lubricating oil taken from and returned to the crankcase of anautomotive engine or the like.

Other fields of use are in food-processing plants, in the chemicalindustry, in steam engines, in systems for supplying oil as a fuel or amotive fluid to internal-combustion (e.g. Diesel) engines or tohydraulic machinery.

. In heat exchangers in which one of the fluids (e.g. oil) isconsiderably more viscous than the other, it is customary to let thisfluid pass along a substantially straight path and at a relatively slowrate through an elongated, generally cylindrical chamber and to conductthe other, more mobile fluid (e.g. water, steam, air or some other gas)through one or more pipes of undulating or helical shape designed toincrease the residence time of the latter fluid in the chamber. It isalso the practice, for more eflicient heat exchange, to let the twofluids move in counterflow to each other. a

These techniques, however, are not always completely satisfactory,particularly when heat is to be extracted from a relatively viscousliquid, such as oil, having a low heattransfer coefiicient (a). Such aliquid, on being chilled by contact with the thermally conductive pipescarrying the colder fluid, tends to congeal into a relatively sluggishboundary layer covering the outer pipe surfaces and mini: m-izing, byreason of its own low thermal conductivity, the transfer of heat fromthe more remote portions of the hot liquid to the cooling pipes. Thisnot only lowers the efliciency of the system but is objectionable inmany instances on account of the lack of homogeneity of the dischargedliquid with reference to, say, its lubricating qualities.

It is, therefore, the general object of the present invention to providean improved heat exchanger which avoids the aforestated disadvantagesand which is particularly, though not exclusively, useful in conjunctionwith viscous fluids of low heat-transfer coeflicient.

This object is realized, in accordance with our invention, by theprovision of a heat exchanger whose elongated, preferably cylindricalhousing, forming a channel for a first fluid, contains a thermallyconductive structure including a plurality of coaxial helicoidalelements of alternating direction of pitch, this structure beingconstituted at least in part by a conduit or conduits carrying a secondfluid in heat-exchanging relationship with the first fluid; thehelicoidal elements, which may be fluid-carrying pipes and/or ribsmounted on the outer surfaces of such pipes, subdivide the elongatedchannels into a plurality of intercommunicating helicoidal zones whichdeflect the first fluid from its linear path and force it to move withboth radial and tangential velocity components so that turbulence isimparted to this fluid and the deposition of a sluggish boundary layeris substantially prevented.

The term helicoidal is used in this context to describe coiledconfigurations of a generally helical nature wherein the spacing andother dimensions of successive turns are not critical and need not beuniform.

FIG. 1 is a longitudinal sectional view of a heat eX- changer accordingto a first embodiment;

FIG. 2 is a fragmentary view of a second embodiment, shown partly inaxial section and partly in elevation;

FIG. 3 is a partly sectional and partly elevational view of a thirdembodiment; and

FIG. 4 is a fragmentary view of a modification of the structure shown inFIG. 2.

In the several views of the drawing, A designates a first fluid, whichmay be a relatively viscous liquid such as oil, whereas B identifies asecond fluid which may be a more mobile liquid or gas.

In FIG. 1 there is shown a heat exchanger whose housing 1 has acylindrical peripheral wall with frustoconical ends terminating in apair of axially aligned ports 1a, 1a for the admission and discharge ofthe fluid A. Extending axially within the housing 1, and supportedtherein by means of radial stays 2a, is a solid elongated core 2 of adiameter substantially equal to that of the ports 1a, 1a. Core 2 issurrounded by an inner tier of helicoidally interleaved pipes 3 of goodthermal conductivity which are spaced apart to define a multithreadhelicoidal path around the core; these pipes 3, in turn, are encasedwithin a second tier of similar pipes 4 which are coiled in the oppositedirection but have substantially the same spacing and pitch angle as theformer. The multithread helicoidal path defined by the pipes 4communicates at numerous locations with the flow path formed by thepipes 3 so that the fluid stream A will distribute itself throughout thehousing and will be turbulently deflected in three dimensions beforeexiting from outlet port 1a.

A second fluid B may traverse all the interleaved and nested pipes 3, 4in series or in parallel; as shown in FIG. 1, fluid enters one of theinner conduits 3 and leaves one of the outer conduits 4 in the vicinityof port 1a so that part of this fluid flows countercurrent to fluid A.

In FIG. 2 there is shown a modified housing whose cylindrical peripheralwall 21 is formed at opposite ends with lateral inlet and outlet ports21b (only one shown) for the fluid stream A; a conical transversepartition 6 at each end of cylindrical wall 21 has apertures 21a leadingto respective helicoidal pipes 3', 3", 4 and 4" which surround astraight central tube v5 and are disposed in four nested tiers ofalternate pitch direction. Adjoining each end of the cylindrical housingwall 21, and secured to it by rivets or other fasteners 22, is afrustoconical end wall 7 with a respective entrance or exit port, onlythe end wall carrying the entrance port 7a being shown in this figure.Fluid B, introduced into port 7a, enters the confronting open end oftube 5 as well as the apertures 21a leading to the pipes 3', 3", 4' and4", traversing all these conduits in its passage toward the exit port atthe opposite end of the housing. The thermally conductive structureconstituted by these conduits again serves to deflect the fluid A,moving in counterflow to fluid B, in a swirling flow onto a path of manyhelicoidal and radial branches.

The embodiment of FIG. 3 comprises a housing 31, generally similar tohousing 1 of FIG. 1, whose frustoconical end walls are penetrated byinlet and outlet ducts 8, 8 for the fluid A that open into an innerspace defined by a generally cylindrical partition 9 which parallels thewall of housing 31 and forms therewith an annular channel 32 for thepassage of fluid B; the latter is admitted into this channel by way of alateral inlet port 31b, and, in flowing toward a lateral exit port 3111'at the opposite housing end, partly traverses a pipe 10 which extendsfor the most part axially within housing 31 as a bypass to channel 32.The outer periphery of pipe 10 and the inner periphery of partition 9carry respective helicoidal ribs 11, 12 of opposite pitch directionwhich again divide the space occupied by fluid A into a plurality ofnested helicoidal zones. Naturally, the entire integral structure 9-12is made of a highly heat-conductive metal, e.g. copper or stainlesssteel, to facilitate heat exchange between the two fluids.

The provision of helicoidal fins or ribs on a conduit for fluid B,designed to deflect the external fluid A as illustrated in FIG. 4 amodification of the system of FIG. 2 wherein a central tube 45, providedwith helicoidal ribs 45a, replaces the plain tube 5 surrounded by theinner tier of helicoidal pipes 3. Moreover, if desired, these helicoidalpipes (or those of the system of FIG. 1) could also be provided, inwhole or in part, with such external helicoidal ribs.

A heat exchanger according to this invention may be directly connected,by its axial ports such as those shown at 1a, 1a, or 8, 8', in apipeline carrying one of the fluids to be heated or cooled. We havefound that, by virtue of the present improvement, the volume of suchheat exchangers is only about a third or a fourth of that ofconventional devices of comparable heat-exchanging capacity and that therate of flow for the control fluid B is similarly reduced.

It may be mentioned that a system of the type as shown in FIG. 2, withseparate cylindrical and frustoconical housing sections 21 and 7, may beextended at will by the insertion of addional cylindrical sectionsthrough which the fluid B passes in succession; fluid A may be led intothe several housing sections by suitable external connections betweentheir respective side ports 21b. Such a system may also be used, forexample, as a water heater of considerably greater compactness thanconventional boilers, with the water (fluid B) entering and leavingaxially via ports 7a and manifolds 6 while the hot combustion gases(fluid A) from a fire chamber are introduced and withdrawn laterally viaports 21b. Conversely, the system of FIG. 2 may also be utilized as acondenser for live steam, with cooling water B introduced at 7a and withthe discharge port 21b turned downwardly to serve as a drain forcondensate A. A further use would be in a refrigeration orair-conditioning system with the air circulated as the fluid A while asuitable coolant is employed as the fluid B. Naturally, the devicesshown in FIGS. 1 and 3 may be utilized in analogous manner for similarpurposes.

The system of FIG. 3 is particularly adapted for the cooling of gases.Fluid A, for example, may be a gas to be fractionated by selectivecondensation of some higherboiling constituent thereof.

The arrangements specifically described and illustrated are, of course,capable of various modifications without departing from the spirit andscope of our invention as defined in the appended claims.

We claim:

1. A heat exchanger comprising an elongated housing forming a channelfor a first fluid, first inlet and outlet means on said housingcommunicating with said channel, thermally conductive conduit meanstraversing said housing in a generally longitudinal direction andforming a path for a second fluid in heat-exchanging relationship withsaid first fluid, and second inlet and outlet means on said housing atthe ends of said path, said conduit means forming part of a thermallyconductive structure including a plurality of alternately crossingcoaxial helicoidal tubes in turns of opposite senses which extend withinsaid channel between said second inlet and outlet and subdivide saidchannel into a plurality of intercommunicating baflies wherebyturbulence is imparted to said first fluid, said coaxial helicoidaltubes forming a packing substantially filling said channel and formingnarrow interstices therebetween for the passage of said first fluid.

2. A heat exchanger as defined in claim 1 wherein said housing has asubstantially cylindrical peripheral wall and a pair of substantiallyconical end walls adjoining said peripheral wall, said end walls havingvertices provided with ports forming part of one of said inlet andoutlet means for the admission and discharge of one of said fluids.

3. A heat exchanger as defined in claim 1 wherein said structureincludes a central member surrounded by said tubes and extending axiallywithin said peripheral walls.

4. A heat exchanger as defined in claim 3 wherein said member is a solidcore.

5. A heat exchanger as defined in claim 3 wherein said member is a tubeopen toward said ports.

6. A heat exchanger as defined in claim 2 wherein said ports form partof said first inlet and outlet means, said conduit means being providedwith terminations constituting said second inlet and outlet means andextending laterally from said housing for the introduction andwithdrawal of said second fluid.

References Cited UNITED STATES PATENTS 1,769,265 7/1930 Labus 163 X1,852,490 4/1932 Sullivan 165156 X 1,893,484 1/1933 Belt 1651S6 X2,888,251 5/1959 Dalin 165-156 X FOREIGN PATENTS 453,328 12/1948 Canada.

621,980 9/1961 Canada.

585,917 11/1958 Italy.

ROBERT A. OLEARY, Primary Examiner. A. W. DAVIS, Assistant Examiner.

1. A HEAT EXCHANGER COMPRISING AN ELONGATED HOUSING FORMING A CHANNELFOR A FIRST FLUID, FIRST INLET AND OUTLET MEANS ON SAID HOUSINGCOMMUNICATING WITH SAID CHANNEL, THERMALLY CONDUCTIVE CONDUIT MEANSTRAVERSING SAID HOUSING IN A GENERALLY LONGITUDINAL DIRECTION ANDFORMING A PATH FOR A SECOND FLUID IN HEAT-EXCHANGING RELATIONSHIP WITHSAID FIRST FLUID AND SECOND INLET AND OUTTLET MEANS ON SAID HOUSING ATTHE ENDS OF SAID PATH, SAID CONDUIT MEANS FORMING PART OF A THERMALLYCONDUCTIVE STRUCTURE INCLUDING A PLURALITY OF ALTERNATELY CROSSINGCOAXIAL HELICOIDAL TUBES IN TURNS OF OPPOSITE SENSES WHICH EXTEND WITHINSAID CHANNEL BETWEEN SAID SECOND INLET AND OUTLET AND SUBDIVIDE SAIDCHANNEL INTO A PLURALITY OF INTERCOMMUNICATING BAFFLES WHEREBYTURBULENCE IS IMPARTED TO SAID FIRST FLUID, SAID COAXIAL HELICOIDALTUBES FORMING A PACKING SUBSTANTIALLY FILLING SAID CHANNEL AND FORMINGNARROW INTERSTICES THEREBETWEEN FOR THE PASSAGE OF SAID FIRST FLUID.